The next thing on the list was the broken fin on the barrels. I cut out a similar shape from some old aluminium that was lying around, then filed it somewhere near. I wanted the barrels to be hot before welding to avoid cracks etc., so a trip to the oven was in order. Half an hour at 150 Celsius was perfect and the liners slid straight out. This was even better because No.4 sat slightly proud before I started.